| From: | Peter Geoghegan <pg(at)bowt(dot)ie> |
|---|---|
| To: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Stephen Frost <sfrost(at)snowman(dot)net>, Jeff Davis <pgsql(at)j-davis(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Bruce Momjian <bruce(at)momjian(dot)us>, Robert Haas <robertmhaas(at)gmail(dot)com>, David Rowley <dgrowleyml(at)gmail(dot)com>, Justin Pryzby <pryzby(at)telsasoft(dot)com>, Melanie Plageman <melanieplageman(at)gmail(dot)com>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Default setting for enable_hashagg_disk |
| Date: | 2020-07-10 21:27:14 |
| Message-ID: | CAH2-Wz=LjdJ+iedXN67g4VRwn6GHzmEGU-7gCKCFMN_XJwLhEA@mail.gmail.com |
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| Lists: | pgsql-docs pgsql-hackers |
On Fri, Jul 10, 2020 at 2:10 PM Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> wrote:
> I'm not sure about this bit; sounds a bit like what has been qualified
> as "nannyism" elsewhere. Suppose I want to give a hash table 2GB of
> memory for whatever reason. If my work_mem is default (4MB) then I
> cannot possibly achieve that without altering both settings.
>
> So I propose that maybe we do want a maximum value, but if so it should
> be higher than what you propose. I think 10000 is acceptable in that it
> doesn't get in the way.
That's a good point.
I amend my proposal: the maximum allowable value of
hash_mem_multiplier should be 10000.0 (i.e., ten thousand times
whatever work_mem is set to, which is subject to the existing work_mem
sizing restrictions).
--
Peter Geoghegan
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